| An option for increasing the efficiency of power transmission and overcoming the difficulties in obtaining new right-of-ways is to construct a high voltage DC power line adjacent to existing AC lines. This kind of configuration is referred to as a hybrid line. When the AC and DC lines are operated close to each other, corona interactions between the energized AC and DC lines need to be studied. TV interference, radio interference, audible noise, ozone generation, ion flow electrification phenomena and corona loss are the problems associated with corona on AC or DC lines, as well as on hybrid lines. The ion flow electrification phenomena can be evaluated by the aid of the profiles of the ground level DC electric field strength and ion current density under the lines. Corona loss and corona current are relevant in power line design.; Reduced-scale modeling technique and computer simulation were used for the study. In 1991-1992, a hybrid single phase AC: and monopolar DC model was built. The linear scale factor of this model was 1:20. In 1993-1994, another reduced-scale model with a linear scale factor of 1:33.3 was constructed. Hybrid three phase AC and bipolar DC line configurations can be utilized by the new scale model.; A calculation method was proposed for the hybrid corona study. In the proposed method, the effect of the applied AC voltage on DC conductor corona activities is included by the fact that the DC conductor corona onset voltage changes with the applied AC voltage. DC corona activities on the AC conductor are also considered. A digital simulation program was implemented to study hybrid single phase AC and monopolar DC corona effects.; The ground level DC electric field strength and ion current density, conductor corona currents in both AC and DC conductors were investigated for various hybrid line configurations. The effects of power line configurations, conductor corona onset voltages, conductor AC and DC voltages, and applied DC voltage polarity on the hybrid line corona were studied by reduced-scale model experiments and the developed computer program. |
